Merge pull request #368 from alphagov/shw-add-disk-space-status-check

Add disk space check for healthcheck

dmutils/__init__.py

@@ -4,4 +4,4 @@
 import flask_featureflags  # noqa
 
 
-__version__ = '34.5.0'
+__version__ = '34.6.0'

dmutils/status.py

@@ -1,5 +1,6 @@
-import os
 import datetime
+import math
+import os
 from .formats import DATE_FORMAT
 from flask_featureflags import FEATURE_FLAGS_CONFIG
 
@@ -26,6 +27,19 @@ def get_flags(current_app):
     return flags
 
 
+def get_disk_space_status(low_disk_percent_threshold=5):
+    """Accepts a single parameter that indicates the minimum percentage of disk space which should be free for the
+    instance to be considered healthy.
+
+    Returns a tuple containing two items: a status (OK or LOW) indicating whether the disk space remaining on the
+    instance is below the threshold and the integer percentage remaining disk space."""
+    disk_stats = os.statvfs('/')
+
+    disk_free_percent = 100 - int(math.ceil(((disk_stats.f_bfree * 1.0) / disk_stats.f_blocks) * 100))
+
+    return 'OK' if disk_free_percent >= low_disk_percent_threshold else 'LOW', disk_free_percent
+
+
 def enabled_since(date_string):
     if date_string:
         # Check format like YYYY-MM-DD

tests/test_status.py

@@ -0,0 +1,29 @@
+from collections import namedtuple
+
+import mock
+import pytest
+
+from dmutils.status import get_disk_space_status
+
+
+def statvfs_fixture(total_blocks, free_blocks):
+    statvfs = namedtuple('statvfs', 'f_blocks f_bfree')
+    return statvfs(total_blocks, free_blocks)
+
+
+@mock.patch('dmutils.status.os.statvfs')
+@pytest.mark.parametrize('kwargs, total_blocks, free_blocks, expected_status',
+                         (
+                             ({}, 1024, 0, ('OK', 100)),
+                             ({}, 1024, 512, ('OK', 50)),
+                             ({}, 1024, 920, ('OK', 10)),
+                             ({}, 1024, 1000, ('LOW', 2)),
+                             ({}, 1024, 1024, ('LOW', 0)),
+                             ({'low_disk_percent_threshold': 10}, 1024, 950, ('LOW', 7)),
+                             ({'low_disk_percent_threshold': 20}, 1024, 920, ('LOW', 10)),
+                             ({'low_disk_percent_threshold': 75}, 1024, 512, ('LOW', 50)),
+                         ))
+def test_disk_space_status(disk_usage, kwargs, total_blocks, free_blocks, expected_status):
+    disk_usage.return_value = statvfs_fixture(total_blocks, free_blocks)
+
+    assert get_disk_space_status(**kwargs) == expected_status